Two-piece molded fan

ABSTRACT

A two-piece molded fan assembly is produced having overlapping fan blades using an axial draw technique. The two halves are then removed from the mold and coupled together to form the two-piece fan. By molding the fan as two pieces, a fan blade can be produced that wraps around the outside of the housing and overlaps with each other in a quick and easy manner using a simple mold design. The two pieces are formed such that the a portion of each overlapping blade is formed on both halves of the assembly so that the die casting tool can be removed along a central axis defining the fan assembly without contacting the respective portion of the fan blades, therein greatly simplifying the manufacturing techniques.

TECHNICAL FIELD

[0001] The invention relates generally to fan drive systems and morespecifically, fan drive systems with two-piece molded fans.

BACKGROUND ART

[0002] Cooling systems are used on vehicles today to provide cooling toan engine during operation. A typical cooling system comprises a waterpump and a fan drive. Fan drives are typically driven by the enginecrankshaft at a fixed ratio to cool engine coolant as it flows through aradiator. More specifically, a fan that is rigidly mounted to the fandrive generates the airflow as a function of engine crankshaftrotational speed for cooling the radiator.

[0003] One important consideration with fans is the ease of manufacture.In automotive applications, molded plastic parts with a minimum numberof parts and assembly steps are generally most cost effective. As willbe recognized by those of skill in the molding art, one of the most costeffective ways to mold plastic is by the so called axial draw techniqueor by pass molding technique, which uses only two molds that part alonga natural axis of the component. The ultimate in fan simplicity usingthis technique is a one-piece fan design. In order to be moldable bythat technique, the part must have a certain structural relationshiprelative to its central axis, such as the central axis of the fan. All“upper” and “lower” surfaces of the part must be divisible in such a waythat they have no radial overlap with one another. If so designed, allpart surfaces may be divided up so that some can be molded by one die,and the rest by the other die, and the pair of die (or molds) can bepushed together and pulled apart freely along the same central axis.This represents the absolute minimum in terms of molds used (two) toproduce the parts, and the number of pieces (one) in the part produced.

[0004] As will be recognized by those of skill in the art, the number offan blade configurations that can be made using a one-piece mold is thuslimited to configurations that can be pulled apart freely along the samecentral axis. For example, overlapping blade fans cannot currently bemade using the axial draw technique because the blade overlap wouldprevent part removal if the whole fan was cast as one piece.

[0005] It is thus highly desirable to introduce a overlapping blade fanusing the axial draw technique.

SUMMARY OF THE INVENTION

[0006] The above and other objects of the invention are met by thepresent invention. In the present invention, a two-piece fan integratedwith the fan drive is produced having overlapping fan blades using anaxial draw technique. The two halves are then removed from the mold andbolted together to form the two-piece fan.

[0007] By molding the fan as two pieces, a fan blade can be producedthat wraps around the outside of the housing and overlaps with eachother. The molding can be done within one die casting tool having afront and rear section or can be done with two separate die castingtools.

[0008] Other features, benefits and advantages of the present inventionwill become apparent from the following description of the invention,when viewed in accordance with the attached drawings and appendedclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a perspective view of a two-piece fan assembly accordingto one preferred embodiment of the present invention;

[0010]FIG. 2 is an exploded view of the two-piece fan assembly;

[0011]FIG. 3 is a front view of FIG. 1; and

[0012]FIG. 4 is a side view of FIG. 1 indicating mold releasedirections.

BEST MODE(S) FOR CARRYING OUT THE INVENTION

[0013] Referring now to the drawings, which are not intended to limitthe invention, FIGS. 1-4 indicates a two-piece fan assembly 10 accordingto a preferred embodiment of the present invention. The two-piece fanassembly 10 is generally defined about a central axis A, and also spinsabout the same axis in operation. The two-piece fan assembly 10 ispreferably formed of die cast aluminum or molded plastic, although othermaterials may be used as those of skill in the art recognize.

[0014] The structural foundation of the fan assembly 10 is the centralhub 12, which is basically an annular disk that extends radially outwardfrom a center bore 14. The center bore 14 is the attachment point of amotor shaft (not shown) that spins the fan assembly 10 about centralaxis A. The motor shaft, and associated housing, have a conventionalarrangement well known to those of skill in the art and will not bediscussed further in this application.

[0015] Disposed about the central hub 12 are a plurality ofcircumferentially displaced, radially disposed fan blades 16 having aradially inner portion 32 of their bases integrally molded with, andsupported by, the central hub 12. Also note that each fan blade 16 has apart of the front side portion 34 blocked by the next adjacent frontside portion 34 when a person views the fan blade 16 from the side as inFIG. 3 (i.e. there is at least a partial overlap of the blades 16 asviewed from the front or back). This overlapping blade 16 structure, asone of skill in the art appreciates, enables the fan assembly 10 toprovide increased air flow as compared with fan assemblies havingnon-overlapping blade structures.

[0016] The fan assembly 10 consists of a front portion 20 (left half ofFIG. 4) and a rear portion 22 (right half of FIG. 4) fastened togetherthrough a coupling device known to those of skill in the art. Both thefront portion 20 and rear portion 52 have a substantially flat region 50a, 50 b that is defined by and corresponding to the relative positioningplane 52. As such, the central hub 12 consists of a front hub portion 12a and a rear hub portion 12 b. Similarly, the fan blades 16 consist of afront fan blade portion 16 a and a rear fan blade portion 16 b. As bestseen in FIG. 4, each front fan blade portion 16 a is coupled to a rearfan blade portion 16 b such that they form a relatively smooth couplingalong and between each radially outward portion 30, radially inwardportion 32, front side portion 34 and rear side portion 36 when thefront portion 20 is coupled to the rear portion 22.

[0017] In the preferred embodiments as shown in FIGS. 1-4, the frontportion 20 and rear portion 22 are formed with a plurality of bolt holes25 a, 25 b. Of course, the boltholes 25 a, 25 b could also be formed ina post-casting step using a drill or similar equipment.

[0018] As best shown in FIG. 4, to couple the front portion 20 to therear portion 22, the flat portions 50 a, 50 b are first aligned alongeither side of the relative positioning plane 52. A bolt 24 is theninserted through a corresponding bolthole 25 a and 25 b to secure thefront portion 20 to the rear portion 22. The bolt 24 may be securedwithin the respective pair of boltholes 25 a, 25 b by a correspondingnut (not shown) or other methods well known in the art. While theembodiments shown in FIGS. 1-4 indicate 12 bolts 24 and 12 correspondingbolt holes 25 a, 25 b circumferentially placed around the hub portions12 a, 12 b, the number and location of the bolts 24 and bolt holes 25 a,25 b may vary as one of skill in the art would appreciate. Further,while the bolts 24 are shown with their head portions 24 a, closelycoupled with the front portion 20, one of skill would recognize that itis equally plausible that the bolt 24 is secured with the head portion24 a closely coupled with the rear portion 22 to secure the frontportion 20 to the rear portion 22.

[0019] Referring now to FIG. 4, the fan assembly 10 is formed by diecasting the front portion 20 and rear portion 22 as two separate pieceswithin a corresponding die casting tool separated along a relativepositioning plane 52. After introduction of the molten material and diecasting has occurred within the die cast tool (not shown) byconventional techniques, the die cast tool separates, as indicated bythe arrows, along the axis A away from the relative positioning plane52, thereby allowing the two portions 20, 22 to be removed from thetooling. As one of skill would recognize, the overlapping structure ofthe fan blades 16 would prevent part removal if the fan assembly 10 werecast as a single part using an axial draw technique. Here, the frontsection of the die cast tool separates from the front portion 20 alongthe axis A away from the relative positioning plane 52 such that thefront section of the tool does not contact the front section of theoverlapping blades 16 a. At the same time, the rear section of the diecast tool separates from the rear portion 22 along axis A away from therelative positioning plane 52 such that the rear section does notcontact the rear section of the overlapping blades 16 b.

[0020] Of course, as is appreciated by one of skill in the art, thefront portion 20 and rear portion 22 could be formed within two separatedie casting tools using the axial draw technique.

[0021] Thus, the present invention presents a simple, easy and efficientprocedure for casting a fan assembly 10 having an overlapping fan blade16 structure using an axial draw technique. Importantly, the techniquepresented in the present invention can be applied to a potentiallyinfinite variety of overlapping fan blade designs. All that is requiredto incorporate this technique is to determine a relative positioningplane 52 within the fan assembly 10 cutting through the fan blades 16and hub 12 such that the die cast tool can be pulled apart along theaxis A of the fan assembly 10 after the portions 20, 22 are die cast.

[0022] While the invention has been described in connection with oneembodiment, it will be understood that the invention is not limited tothat embodiment. On the contrary, the invention covers all alternatives,modifications, and equivalents as may be included within the spirit andscope of the appended claims.

What is claimed is:
 1. A method for forming a fan assembly defined byand capable of spinning about a central axis, said fan assembly having aplurality of circumferentially displaced, radially disposed overlappingfan blades coupled about a central hub, the method comprisingcomprising: determining a relative positioning plane extending throughthe plurality of overlapping fan blades and central hub of the fanassembly, said relative positioning plane located such that a frontportion of said plurality of overlapping fan blades are located on oneside of the relative positioning plane a rear portion of said pluralityof overlapping fan blades are located on the opposite side of saidrelative positioning plane; die casting said front portion of the twopiece fan assembly, said front portion having said first portion of saidplurality of overlapping fan blades and a front hub portion and asubstantially flat front flat portion, said front flat portion definedby said relative positioning plane; die casting a rear portion of thetwo piece fan assembly, said rear portion having said second portion ofsaid plurality of overlapping fan blades and a rear hub portion and asubstantially flat rear flat portion, said rear flat portion defined bysaid relative positioning plane; and coupling said front portion to saidrear portion to form the two-piece fan assembly.
 2. The method of claim1, wherein die casting a front portion and die casting a rear portioncomprises: introducing a first quantity of a molten material within saidfront portion of a die casting tool; introducing a second quantity ofsaid molten material within said rear portion of said die casting tool;and cooling said first quantity of cast molten material to form saidfront portion and cooling said second quantity of cast molten materialto form said rear portion.
 3. The method of claim 1, wherein said fronthub portion has a plurality of bolt holes formed therein and whereinsaid rear hub portion has a second plurality of holes formed therein. 4.The method of claim 2, wherein coupling said front portion to said rearportion comprises: providing a plurality of bolts, each of saidplurality of bolts having a head; forming a plurality of front boltholes on said front hub portion in a post-casting step; forming a secondplurality of rear bolt boles on said rear hub portion in a post-castingstep; coupling said front flat portion of said front portion to saidrear flat portion of said rear portion; introducing one of saidplurality of bolts through a corresponding one of said plurality offront bolt holes and through a corresponding one of said secondplurality of rear bolt holes, wherein at least one of said heads of saidplurality of bolts is closely coupled with said front hub portion; andsecuring each of said plurality of bolts.
 5. The method of claim 2,wherein coupling said front portion to said rear portion comprises:providing a plurality of bolts, each of said plurality of bolts having ahead; forming a plurality of front bolt holes on said front hub portionin a post-casting step; forming a second plurality of rear bolt boles onsaid rear hub portion in a post-casting step; coupling said front flatportion of said front portion to said rear flat portion of said rearportion; introducing one of said plurality of bolts through acorresponding one of said second plurality of rear bolt holes andthrough a corresponding one of said plurality of front bolt holes suchthat at least one of said heads is closely coupled with said rear hubportion; and securing each of said plurality of bolts.
 6. The method ofclaim 4, wherein securing said plurality of bolts comprises securingeach of said plurality of bolts with a corresponding nut, saidcorresponding nut closely coupled with said rear hub portion.
 7. Themethod of claim 5, wherein securing said plurality of bolts comprisessecuring each of said plurality of bolts with a corresponding nut, saidcorresponding nut closely coupled with said front hub portion.
 8. Themethod of claim 3, wherein coupling said front portion to said rearportion comprises: providing a plurality of bolts, each of saidplurality of bolts having a head; coupling said front flat portion ofsaid front portion to said rear flat portion of said rear portion;introducing one of said plurality of bolts through a corresponding oneof said plurality of front bolt holes and through a corresponding one ofsaid second plurality of rear bolt holes, wherein at least one of saidheads of said plurality of bolts is closely coupled with said front hubportion; and securing each of said plurality of bolts.
 9. The method ofclaim 3, wherein coupling said front portion to said rear portioncomprises: providing a plurality of bolts, each of said plurality ofbolts having a head; coupling said front flat portion of said frontportion to said rear flat portion of said rear portion; introducing oneof said plurality of bolts through a corresponding one of said secondplurality of rear bolt holes and through a corresponding one of saidplurality of front bolt holes such that at least one of said heads isclosely coupled with said rear hub portion; and securing each of saidplurality of bolts.
 10. The method of claim 8, wherein securing saidplurality of bolts comprises securing each of said plurality of boltswith a corresponding nut, wherein said corresponding nut is closelycoupled with said rear hub portion.
 11. The method of claim 9, whereinsecuring said plurality of bolts comprises securing each of saidplurality of bolts with a corresponding nut, wherein said correspondingnut is closely coupled with said front hub portion.
 12. A method for diecasting a two-piece fan assembly having a plurality of circumferentiallydisplaced, radially disposed overlapping fan blades, said fan assemblycapable of rotating about a central axis, the method comprising:determining a relative positioning plane extending through the pluralityof overlapping fan blades and central hub of the fan assembly, saidrelative positioning plane located such that a front portion of saidplurality of overlapping fan blades are located on one side of therelative positioning plane a rear portion of said plurality ofoverlapping fan blades are located on the opposite side of said relativepositioning plane; die casting a front portion and a rear portion of thetwo piece fan assembly within a die casting tool having a front sectionand a rear section, wherein said front portion having said first portionof said plurality of overlapping fan blades and a substantially flatfront flat portion, said front flat portion defined by said relativepositioning plane, wherein said rear portion having said second portionof said plurality of overlapping fan blades and a substantially flatrear flat portion, said rear flat portion defined by said relativepositioning plane; uncoupling said front section of said die cast toolalong said central axis away from said relative positioning plane suchthat said front section does not contact first portion of said pluralityof overlapping blades; and uncoupling said rear section of said die casttool along said central axis away from said relative positioning planesuch that said rear section does not contact second portion of saidplurality of overlapping blades.
 13. The method of claim 12, wherein diecasting a front portion and die casting a rear portion comprises:introducing a first quantity of a molten material within said frontsection; introducing a second quantity of said molten material withinsaid rear section; and cooling said first quantity of cast moltenmaterial to form said front portion and cooling said second quantity ofcast molten material to form said rear portion.
 14. The method of claim12, wherein said front hub portion has a plurality of bolt holes formedtherein and wherein said rear hub portion has a second plurality ofholes formed therein.